After opening with a bogey on the first, Smyth reached the turn one over par after picking up two birdies on the second and eighth holes but then dropping further shots on the fifth and ninth.

However a steadier back nine saw the 58 year old from Drogheda birdie the 11th, 13th and 17th holes to make an impressive start to the season’s first Senior Major Championship.

Murota is one stroke clear of America Trevor Dodds with former Open Champion Mark O’Meara a further shot back on four under par after a 68.

Five time Open Champion Tom Watson is also in contention on a day that was affected by severe storms which battered Louisville.

Watson is level with Smyth on four under par, along with former World Number One Nick Price.

“Two under is a good score,” said Watson. “It's not easy to play under wet conditions and stop and start. It's not easy. But we have done it before and there are no surprises out there. It was just a long day and you just had to be prepared for the second go around, which I did.

“I played a good round of golf. I think I played a little bit better than I scored today. I made some errors on the greens with the putter and I'm very happy about the way I struck a lot of my long irons.”

Boonchu Ruangkit, the 2010 European Senior Tour Order of Merit winner, had five holes of his round remaining before play was suspended for the day. The Thai was one under par through 13 holes, as was fellow Senior Tour Member Mike Harwood who completed 11 holes.

Current Senior Tour Order of Merit leader Sandy Lyle struggled with the conditions at the start of his round, opening with three bogeys and two double bogeys in his first seven holes before picking up his first birdie of the day before the suspension to be six over par after eight holes.